Hepa filters work best

To stand out in the market, many new air purifiers come with bells and whistles.

Besides their main function of removing dust particles, manufacturers say that some can also humidify the air to relieve sinus problems or ionise it to remove bacteria and viruses. Others double as fans or mosquito catchers.

The range is so wide that it is enough to give consumers a headache, haze or no haze. But experts say that when shopping for an air purifier, the most important thing to look out for is a high efficiency particulate air (Hepa) filter.

Dr Steve Yang, 44, a respiratory specialist at Raffles Internal Medicine Centre, says: "Only these can filter out the very small particles, those 0.1 to 0.3 microns in size."

The Government's haze microsite (www.haze.gov.sg) says the main air pollutant during bouts of haze in Singapore is particulate matter. Other pollutants include sulphur dioxide, ozone, nitrogen dioxide and carbon monoxide.

Experts say particulate matter ranges in size, but fine particulate matter - with a diameter of less than 2.5 microns - is particularly harmful. A Hepa filter can filter these particles easily.

Consumers can refer to the Government's haze website for a list of portable air cleaners available in the market.

Purifiers are available at major appliance stores such as Best Denki, Courts, Gain City and Harvey Norman. Prices range from $99 to more than $1,000 each.

When asked, experts declined to comment on the effectiveness of individual brands and models.

Associate professor Rajasekhar Balasubramanian, 53, from the National University of Singapore's department of civil and environmental engineering, says: "Little research has been done on the effectiveness of air cleaners.

"A systematic study is needed to evaluate and compare the performance of different portable air- cleaning technologies in terms of their ability to remove a range of indoor air pollutants during the occurrence of smoke haze events."

The Consumers Association of Singapore recommends using an air purifier when there is haze, "especially for those suffering from respiratory diseases, the elderly and the young".

Case executive director Seah Seng Choon, 62, says: "However, if consumers do not have an air purifier, they can close the windows and turn on the air-conditioning to help reduce the amount of haze particles indoors."

Two weeks ago, housewife Inna Angullia, 36, spent almost $1,200 buying two air purifiers with Hepa filters from Courts. She has two children - a son, two, and a three- month-old daughter. Her husband, 26, is a property officer in a town council.

She says: "The haze this time looks like it is going to last much longer than in previous years and now I have two young children."

Before she bought the purifiers for her three-room HDB flat in Tampines, her baby had a flu and cough and was hospitalised for a night earlier this month. Ms Inna also had a sore throat and found it difficult to breathe.

She says: "Thankfully, now it is easier to breathe at home."

Air purifiers

Novita PuriClean NAP 501

Introduced: December 2013

Coverage: 25 sq m

Price: $369

The device has a Hepa filter and a sensor that will diagnose and indicate the current air quality through the display of different colours. It also has an ioniser that can diffuse more than 20 million negative ions to eradicate airborne germs and allergens.

Tefal Intense Pure Air PU4025

Introduced: June this year

Coverage: 35 sq m

Price: $399

The device has four layers of filters, including a Hepa filter. It can trap big pollutants such as dust, human and animal hairs.

It can also dissipate food smells, animal, paint and tobacco odours, and destroy formaldehyde - a chemical emitted by furniture varnish, paint, cleaning products and scented candles - that can cause allergies and respiratory ailments such as asthma.

There is also a larger model - the PU6025 - that covers 80 sq m and sells for $599.

Sharp FP-FM40E-B

Introduced: This month

Coverage: 30 sq m

Price: $459

The device is equipped with three layers of filters, including a Hepa filter.

Apart from cleaning the air, it also doubles as a mosquito catcher. It attracts mosquitoes using its black body and LED UV lights. When mosquitoes rest on the device's narrow air inlet, they are sucked in by the powerful airflow and trapped permanently on a three-layer glue sheet inside.

Dyson Pure Cool

Introduced:April this year

Coverage: A rate of 13 sq m every 25 minutes

Price: $999

Both a fan and an air purifier, this device circulates purified air across the whole room, unlike conventional air purifiers that typically release purified air straight up to the ceiling.

It has a 360-degree Hepa filter that can capture ultra-fine particles as small as 0.1 microns and a layer of activated carbon granules to capture odours and harmful toxins such as paint fumes.

Stick to tested N95

Newfangled masks - some with fancy colours, shapes and designs - and other products that claim to help in the haze have come onto the market.

But experts advise that it is best to stick to masks and products which have been tested and endorsed by appropriate environmental or health organisations.

The Government's haze microsite (www.haze.gov.sg) identifies two categories of masks designed to reduce the exposure to airborne contaminants such as particles and gases.

The first is the N95 mask, which is certified to have 95 per cent filter efficiency by the United States National Institute for Occupational Safety and Health.

These masks are available at major pharmacies and supermarkets such as Unity, Watsons, Cold Storage, FairPrice and Giant.

They come in different brands, colours, shapes and sizes. For example, a box of 20 N95 masks is selling for $38 at Sheng Siong supermarkets.

The second type is the EN-149 mask, which meets a type of European standard for respiratory masks. These can filter 80 to 99 per cent of airborne dust particles and can be bought through the websites of their distributors.

Masks with new features, such as valves to provide easy exhalation, have emerged.

For example, the AIR+ Smart Mask, a certified N95 mask launched in March and selling at $7.20 for a box of three, has a valve for improved air flow.

A small micro ventilator, which costs $29.90, can be attached to the mask to draw out heat, moisture and carbon dioxide, thereby reducing temperatures in the mask by up to 4 deg C.

The 3M 9211 mask, which has a one-way valve and is selling at $3.50 each, was introduced last month.

Mr Edwin Tan, 39, a safety officer in the construction industry who has been using the 3M 9211 mask for the last three weeks, says: "When I wear a mask with no valve, it takes only a few minutes to feel uncomfortable because the heat and moisture accumulate inside the mask.

"When I use a mask with a valve, the exhaled air can leave the mask more easily and it takes twice as long before I feel uncomfortable."

Yet another mask - the Vogmask - which hit the market last year, comes in more than 12 designs.

The reusable mask, which has N95 certification, comes in different prints and features a carbon filter and exhale valve. It is selling at $39 each.

Experts advise that when choosing masks, it is best to stick to tested N95 masks.

Dr Ong Kian Chung, 52, a respiratory medicine specialist at Mount Elizabeth Medical Centre, says: "The standard N95 mask is sufficient for protection against the haze."

Dr Erik Velasco, 41, a research scientist from the Singapore-MIT Alliance for Research and Technology, says: "If a consumer wants to buy other types of masks, I would recommend investigating if such masks have been tested and endorsed by the health authorities."

Besides masks, other creative products in the market also claim to be able to help beat the haze.

A new filter, for example, meant to be wrapped behind the back of a fan, claims to turn fans into air purifiers.

One "air purifier" also claims to use specialised plants to help purify the air of dust and particulates.

Experts were sceptical about such products. Dr Ong says: "I'm not convinced. The onus should be on the manufacturers to prove their claims."

This article was first published on Oct 4, 2015.
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